Intermetallic compounds of certain rare earth and transition metals (RE-TM) can be made into magnetically aligned permanent magnets with coercivities of several thousand Oersteds. The compounds are ground into sub-crystal sized particles commensurate with single magnetic domain size, and are then aligned in a magnetic field. The particle alignment and consequently the magnetic alignment, is fixed by sintering or by dispersing the particles in a resinous binder or low melting metal such as lead. This is often referred to as the powder metallurgy process of making rare earth-transition metal magnets. When treated in this manner, these intermetallic compounds develop high intrinsic magnetic coercivities at room temperature.
The most common intermetallic compounds processable into magnets by the powder metallurgy method contain substantial amounts of the elements samarium and cobalt, e.g., SmCo.sub.5, Sm.sub.2 Co.sub.17. Both of these metals are relatively expensive due to scarcity in the world market. They are, therefore, undesirable components for mass produced magnets. Lower atomic weight rare earth elements such as cerium, praseodymium and neodymium are more abundant and less expensive than samarium. Similarly, iron is preferred over cobalt. However, it is well known that the light rare earth elements and iron do not form intermetallic phases when homogeneously melted together and allowed to crystallize as they cool. Moreover, attempts to magnetically harden such rare earth-iron alloys by powder metallurgy processing have not been successful.
This invention relates to a novel, efficient and inexpensive method which can be used to produce magnetically coercive rare earth-iron alloys directly from homogenous molten mixtures of the elements.